1. Field of the Invention
The present invention relates to a cannula assembly and cannula accessory assemblies for endoscopic and laparoscopic surgical procedures having a portion of the assembly formed of an electrically conductive material.
2. Description of the Related Art
Endoscopic surgical procedures, that is, surgical procedures performed through tubular sleeves or cannulas, have been utilized for many years. Initially, endoscopic surgical procedures were primarily diagnostic in nature. More recently as endoscopic technology has advanced, surgeons are performing increasingly complex and innovative endoscopic surgical procedures. In endoscopic procedures, surgery is performed in any hollow viscus of the body through narrow endoscopic tubes (or cannulas) inserted through small entrance wounds in the skin. In laparoscopic procedures surgery is performed in the interior of the abdomen through a small incision.
Laparoscopic and endoscopic procedures generally require that any instrumentation inserted into the body be sealed, i.e., provisions must be made to ensure that gases do not enter or exit the body through the laparoscopic or endoscopic incision as, for example, in surgical procedures in which the surgical region is insufflated. Moreover, laparoscopic and endoscopic procedures often require the surgeon to act on organs, tissues and vessels far removed from the incision, thereby requiring that any instruments to be used in such procedures be both long and narrow.
Generally, cannulas are currently fabricated from stainless steel. However, radiolucent cannulas are utilized in situations where high quality imaging is required. For example, during an endoscopic cholecystectomy, it is common to perform a cholangiogram by introducing a catheter into the cystic duct. Therefore, surgeons typically employ radiolucent materials, such as plastic or fiberglass, when placing cannulas and cannula accessories in the region of the cholangiogram in order to obtain high quality images of the region.
Comparing stainless steel and fiberglass to a highly conductive material, such as silver, stainless steel has a conductivity value which is twelve percent the conductivity value for silver. Fiberglass has a conductivity value which is less than one percent the conductivity value for silver and is generally considered to be a dielectric. For the purposes of the present disclosure, silver is assumed to be about one hundred percent conductive.
With the recent sophistication and popularity of such endoscopic surgical procedures, a wide array of endoscopic instruments are being utilized in connection therewith. For example, an assortment of instruments include electrocautery capability which may be used to achieve hemostasis. The principle of electrocautery is based upon the resistance to the flow of electrical current through tissue. Such resistance results in heat generation as current attempts to pass therethrough. The degree of resistance to electrical current flow for tissue depends primarily on its vascularity and water content, with bone and fat having a higher resistance to current flow than skin and muscle.
Electrocautery equipment is typically either unipolar or bipolar. In unipolar applications, electrical energy is supplied from a generator to the end of an electrical conductor, e.g., cauterization wire, which is pressed against or placed adjacent the desired surgical site. A grounding plate is typically located below the patient so that the electrical current delivered by the cauterization wire passes through the patient to the plate, thereby completing the electrocautery circuit. In contrast thereto, in bipolar electrocautery equipment, a grounding wire is part of the instrumentation placed against the surgical site and the electrical current passes directly from the cauterization wire, through the tissue at the surgical site, and to the grounding wire thereby completing the electrical circuit.
Recently, concerns have been raised based upon speculation that the introduction and activation of an electrocautery instrument within a stainless steel and/or fiberglass cannula assembly may cause an electrical charge to build on the cannula. Such charge, if not sufficiently dissipated, is thought to potentially cause interference with the electrocautery device, or interference with the patient. During a recent meeting of the FDA's Obstetrics and Gynecology Devices Panel on Apr. 29, 1991, these concerns were discussed. However, no definitive position was taken by the FDA on whether these concerns were legitimate and whether current FDA guidelines on devices and methods associated with electrosurgery should be modified.
In view of these concerns, it is believed desirable to develop technology which would effectively dissipate such charges in the remote possibility that a buildup should occur. For example, commonly assigned U.S. patent application Ser. No. 07/683,253, filed Apr. 10, 1991, relates to a device and method for dissipating electrical energy during such surgical procedures by incorporation of energy dissipation means communicating with electrical conductive means. This application is incorporated herein by reference.
The present invention relates to cannula assemblies and accessories therefor which are fabricated at least in part from highly electrically conductive material which would dissipate such buildup in the event such remote concerns prove founded.